Arguably by 2012, Valve was already transitioning out of the game development business and into the services business. Team Fortress 2 was already out, Left 4 Dead 2 was already out, Portal 2 was already out, Counter-Strike: Global Offensive came out in the same year, and Dota 2 came out the next year. Really the only things that have been made since that period are Half-Life: Alyx (2020), Counter-Strike 2 (2023) and Deadlock (TBA).

They didn't transition out of game development. Dota 2 was under heavy development all these years after it "came out". It was only when Deadlock started heavy development that Dota 2 was winding down.

Everyone forgets about Artifact :).

Dota Underlords came out since then, which is a brilliant game that they effectively abandoned / moved on to Deadlock.